Heretofore, most vaccines have been produced by attenuation or inactivation of viruses and bacteria. However, according to the recent development in genetic recombinant technology, the possibility of recombinant component vaccines utilizing only a gene derived from a specific pathogen is suggested. Actually, the vaccine against hepatitis B virus is produced by recombinant technology.
However, the induction of antigen-specific immune response such as production of an antibody is difficult when an antigen for component vaccine not having an affinity to mucosal tissues is directly administered to mucous membrane. Accordingly, a significant improvement in affinity of vaccine antigens for nasal or intestinal mucous membrane has been tried by fusing mucous membrane-binding proteins such as cholera toxin B subunit (CTB), which have an affinity for mucous membrane, with the vaccine antigens (for example, Japanese Unexamined Patent Application Publication No. 6-206900). However, some antigens are difficult to be produced into such fusion proteins or cannot efficiently function as a vaccine in the form of such fusion proteins.
Furthermore, no fusion protein of a digestive tract mucous membrane-binding protein and an antigen derived from Japanese encephalitis virus has been confirmed to be useful as a Japanese encephalitis vaccine component for producing an antibody.
The present invention has been completed under these circumstances, and an object is to provide a vaccine which can be produced on an industrial scale by improving the production scale and the purification efficiency. Additionally, an object of the present invention is to provide a Japanese encephalitis component vaccine.